CodeForces-115A.py

from collections import *
from math import *
from heapq import *
from itertools import *
from queue import *
from cmath import *
from random import *
from functools import *
from time import *
from typing import *
from numbers import *
from fractions import *
from decimal import *
from cmath import *
import sys
import os

def INPUTS():
   #n = int(sys.stdin.readline().strip())
   #arrary = [int(sys.stdin.readline().strip()) for _ in range(n)]
   SINGLE_INT = lambda:int(input())
   #MINGLE_INT = lambda:map(int,input().split())
   
   #SINGLE_STR = lambda:input().strip()
   # MINGLE_STR = lambda:map(str,input().split())
   
   #LIST_INT = lambda:list(map(int,input().split()))
   # LIST_INT2 = lambda:list(map(int,input().split()))
   # LIST_STR = lambda:list(map(str,input().split()))
     
   #LIST_SORTED = lambda:sorted(list(map(int,input().split())))
   
   return 


def solution():
   a = [-1j]
   ans = 1
   n = int(input())
   for _ in range(n):
      a.append(int(input()))
   for i in range(1,n+1):
      node = a[i]
      dep = 1
      while node!=-1:
         node = a[node]
         dep+=1
      ans = max(ans,dep)
   print(ans)
   
def main():
   # test_cases = int(input())
   
   # for T in range(test_cases):
   #     solution()
      
       #print(f'Case{T+1}:{solution()}')
   solution()

   
   
if __name__ == '__main__':
   main()